Recently, in such technical fields as biotechnology and healthcare, attention is being paid to micro-analysis chips which, by means of fine fluid elements, such as micro flow channels and detection mechanisms, electrically detects fine particles or biopolymers in a sample liquid, or separates such components from the sample liquid. The separation/detection mechanisms of this type of analysis chips often include a mechanism for applying an electrical signal to a sample liquid which has been introduced between electrodes, and/or extracting a characteristic change in a sample liquid as an electrical signal.
However, since the sample liquid directly contacts the electrodes, there is a case where the sample liquid may electrochemically react with the electrodes as a result of the voltage applied across the electrodes, thereby changing the nature of the surfaces of the electrodes. If the electrode surfaces are changed in this way, a problem that a necessary electrical signal is not applied to the sample liquid or a desired electrical signal is not obtained may occur.